Battery gassing is a normal occurrence during charging and storage of batteries. Additionally, hydrogen gas generated during corrosion reactions can increase the internal cell pressure, causing electrolyte leakage and disrupting of the cell integrity. This process is known as “gassing.” Gas generation in alkaline batteries during storage is a result of hydrogen formation in the anode compartment driven by reduction reactions on metallic impurities present in the anode. It is enhanced after partial discharge because the discharge removes the protective surface oxide film. Metallic impurities are inherent to the anode material as contaminants and can also originate from other battery materials such as the cathode, graphite, electrolyte, current collector, or other additives used in the making of alkaline batteries. These impurities may be localized or randomly distributed.
Gassing can lead to several problems in a battery. For example, gassing raises safety concerns due to the explosive hydrogen gas buildup produced. Gassing also causes the consumption of active zinc material, thereby permanently reducing battery capacity. Additionally, gassing also consumes the water in the battery, which is needed for cathode reduction reactions, thereby further decreasing battery capacity. Proposed remedies to offset gassing related problems include designing battery cells with safety vents which will release gas in the event of a pressure buildup, employing corrosion-resistant materials, adding gassing inhibitors or corrosion inhibitors, and minimizing the presence of metallic impurities in the battery cell. The hydrogen gas generated during corrosion reactions leads to internal cell pressure build-up and, ultimately, to electrolyte cell leakage. Organic and inorganic inhibitors commonly used to suppress hydrogen gas generation during storage can drastically suppress discharge performance, making their benefit impractical.